1. Field of the Invention
The present invention relates to an electronic part conveying member to be used for conveyance of a chip type electronic part, or the like, until it is mounted on a board, and a cover tape to be used for the electronic part conveying member.
2. Description of the Related Art
As a common conveyance embodiment for a chip type electronic part, such as a chip fixing resistor, and a laminated ceramic capacitor, a taping reel method using a tape for conveying an electronic part (electronic part conveying member) is known. According to the taping reel method, an electronic part is inserted into electronic part storage pockets provided by a certain distance in the longitudinal direction of a plastic or paper carrier tape, and the electronic part is sealed by thermally sealing the upper surface with a cover tape so as to be wound up on a reel and conveyed. In a production step of a circuit board, or the like after conveyance, after peeling off the cover tape, an automatic assembly system for automatically suctioning the inserted electronic part by an air nozzle for supplying the same onto a board is mainly used.
In a series of steps from taping to the chip supply to a board, a problem is involved in that the electronic part packaged by taping adheres or melts on the tape adhesive layer surface so as not to be picked up by a suction nozzle at the time of peeling off the cover tape. Moreover, recently, according to the trend toward a light weight, a thin and short shape, a small size, and a high function of the electronic parts such as an IC, there is a high risk of deterioration or destruction of the electronic parts due to the static electricity generated by contact with a carrier tape or a cover tape, or the static electricity generated at the time of peeling off a cover tape. Furthermore, due to variation in the peel strength of a cover tape, an electronic part stored at a predetermined position may come out from a storage pocket, or displacement thereof may occur. Therefore, for such a cover tape for the electronic part conveyance, a countermeasure for the static electricity for reducing the contact electrification voltage and the peeling electrification voltage is called for as well as reduction of the peel strength variation is demanded.
As to the static electricity countermeasure, for only providing a conductivity, a method of applying a conductive coating on the adhesive layer surface of a cover tape, or impregnating a cover tape with a conductive agent can be adopted (see JP-A-10-86993). However, according to the method, the adhesive property of the cover tape is lowered, and thus the function of sealing an electronic part cannot be provided sufficiently. Moreover, as a countermeasure for the static electricity, a method of providing an inorganic substance layer comprising an intermediate layer and a metal foil layer or an inorganic deposition layer between a sealant layer (adhesive layer) and a stretched resin layer (substrate) of a cover tape (see JP-A-8-112880), and a method of including or applying conductive fine particles of a metal oxide, or the like, or a carbon black in an adhesive layer or a substrate have been proposed. However, according to the methods, in providing a sufficient conductivity, a problem is involved in that the transparency (light transmittance) of the cover tape is lowered so that confirmation of a tape by visual recognition or an image process is disturbed, or variation in the peel strength of the tape is enlarged.
Accordingly, an object of the invention is to provide a cover tape for the electronic part conveyance having both good conductivity and appropriate adhesive property, capable of preventing electrostatic destruction of an electronic part due to the friction electrification by the vibration, or the like during transportation of the electronic part or by the contact with the cover tape adhesive layer surface, peeling electrification at the time of peeling off the cover tape, or the like, capable of reducing the peel strength variation at the time of peeling off, and capable of preventing projection, or the like of the electronic part from an electronic part conveying member.
Another object of the invention is to provide a cover tape for the electronic part conveyance having a high transparency so as to allow preferable visual recognition of an electronic part, in addition to the above-mentioned characteristics.
Still another object of the invention is to provide an electronic part conveying member comprising a cover tape having the above-mentioned excellent performances.
As a result of elaborate discussion of the present inventors for achieving the above-mentioned objects, it was found that by providing a specific layer between a substrate and an adhesive layer as well as forming a conductive layer on at least one selected from the group consisting of the substrate rear surface and the adhesive layer front surface by deposition, troubles of an electronic part derived from the static electricity can be prevented, variation in the peel strength at the time of peeling off can be reduced, and further, the transparency can be retained so as to complete the invention.
That is, the invention provides a cover tape for the electronic part conveyance comprising laminated members in four or more layers, including at least one selected from the group consisting of a base coating layer and an intermediate layer, and an adhesive layer, laminated successively on a substrate as well as a conductive layer formed on at least one selected from the group consisting of the substrate rear surface and the adhesive layer front surface by deposition.
Moreover, the present invention provides an electronic part conveying member comprising an electronic part storage member for storing an electronic part, and a cover tape for covering the electronic part storage member, wherein the above-mentioned cover tape for the electronic part conveyance is used as the cover tape.